Random linear copolyesters of asymmetrically substituted phthalic acids



United States Patent Ollice 3,365,425 RANDGM LINEAR COPGLYESTERS F ASYM- IXIETRICALLY SUBSTITUTED PHTHALIC ClDS William H. Watson, Grifton, N.C., assignor to E. I. du Pont de Nemonrs and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Apr. 12, 1965, Ser. No. 447,512 3 Claims. (Cl. 260-75) ABSTRACT OF THE DISCLOSURE A linear random copolyester consisting essentially of the condensation copolymer of ethylene glycol with a mixture of 70 to 90 mole percent of bibenzoic acid and 30 to 10 mole percent of a bulky, asymmetrically substituted phthalic acid selected from the group consisting of 2,5-diphenylterephthalic acid, 4,6-diphenylisophthalic acid and S-tert-butyl-isophthalic acid. Also disclosed are fibers and yarns of the above copolyesters having good recovery properties.

This invention relates to a novel class of copolyesters, and to fibers, films and other shaped articles prepared therefrom.

Fibers of synthetic polyesters have achieved wide commercial usage in a great variety of applications because of a particularly advantageous combination of physical properties. Frequently, however, it has been desired to improve one or more of these properties to gain superior performance in certain applications. The search for superior polyesters has included an examination of the polyesters and copolyesters of bibenzoic acid. However, this work has generally not been fruitful because polyesters of bibenzoic acid and a glycol (e.g., polyethylene bibenzoate) are extremely high melting and have high rates of crystallization, making the preparation of useful articles from them extremely difficult and costly.

In accordance with the present invention, novel copolyesters of bibenzoic acid have been found with melting points and rates of crystallization suitable for the formation of fibers, films and other useful shaped articles.

The novel copolyesters of this invention are linear condensation copolymers of ethylene glycol with a mixture of 70-90 mole percent bibenzoic acid and 30-10 mole percent of a bulky, asymmetrically substituted phthalic acid selected from the group consisting of 2,5-diphenyl terephthalic acid, 4,6-diphenylisophthalic acid, and S-tertbutyl-isophthalic acid. In fiber form these copolyesters will have an intrinsic viscosity of at least 0.3, as measured in solution at 25 C. in methylene chloride (80%)-trifiuoracetic acid (20%) (solvent). The invention, however, also contemplates films and other shaped articles prepared from these novel copolyesters.

The novel polymers of the invention may alternatively be characterized as linear random copolyesters having recurring units consisting essentially of those represented by the formulas:

and

where Ar is a bulky, unsymmetrically substituted phenylene radical of the group consisting of Patented Jan. 23, 1368 and wherein the ratio of the units 1/11 is within the range /30 to /10.

The copolyesters in this group are generally stable to conditions used in commercial melt polymerization and spinning techniques, have melting points suitable for melt spinning, and have rates of crystallization which enable them to be readily quenched to form drawable fibers suitable for textile purposes. The fibers are characterized by a high degree of recovery from low tensile strain, a property particularly desired in fibers used in the preparation of wash-and-wear fabrics.

The novel copolyesters of the invention are preferably formed from a mixture of monomeric components including ethylene glycol and a mixture of 70-90 mole percent dimethyl bibenzoate with 30-10 mole percent of a dimethyl ester of an acid from the group consisting of 2,5 diphenylterephthalic acid, 4,6 diphenylisophthalic acid, and S-tert-butylisophthalic acid. Other lower alkyl esters, phenylesters, etc., of the acid may be used in place of the dimethyl ester. The reaction is usually carried out with the assistance of an ester interchange catalyst such as manganous acetate, zinc acetate, calcium acetate, or sodium methoxide. The ester interchange reaction is followed by polycondensation at high temperature and low partial pressure of the glycol until a polymer of the desired molecular weight is produced. Alternatively, the his glycol esters of the acids may be conveniently formed first and then reacted in the desired mole percentages using a polymerization catalyst such as antimony trioxide, litharge, and the tetralkyl titanates, e.g., tetraisopropyl titanate. Similarly, other equivalent methods such as using ethylene oxide in the place of ethylene glycol may be employed so long as the end product copolyester has the composition indicated above.

Alternatively the copolyesters may be formed from ethylene glycol and the acid chlorides of the dicarboxylic acids.

Part of the ethylene glycol may be replaced by other suitable glycols in minor amounts, i.e., up to about 10 mole percent. Examples of suitable glycols include the polymethylene glycols, such as propylene glycol, tetramethylene glycol, hexamethylene glycol, and decamethylene glycol as well as the branched chain glycols, such as 2,2 dimethyl 1,3 propanediol and 2,2 dimethyl 1,4- butanediol. Other suitable glycols include cisand transp-hexahydroxylylene glycol, bis-p-(2-hydroxyethyl)-benzene, diethylene glycol, bis-(4-hydroxybutyl)ether, bis- 1,4-(2-hydroxyethoxy)-benzene, and triethylene glycol. Mixtures of the glycols may be used.

The expression polymer melting temperature employed with respect to the products of this invention is the minimum temperature at which a sample of the polymer leaves a wet molten trail as it is stroked with moderate pressure across a smooth surface of the heated metal. Polymer melting temperature, abbreviated PMT, has sometimes in the past been referred to as polymer stick temperature.

The term intrinsic viscosity, as used herein, is defined as the limit of the fraction ln (r) as e approaches zero, where (r) is the relative viscosity, and c is the concentration in grams per 100 ml. of solution. The relative viscosity (r) is the ratio of the viscosity of a solution of the polymer in a mixture of 80 parts methylene chloride and 20 parts tritluoracetic acid (by volume) to the viscosity of the methylene chloride/trifluoraeetic acid mixture, per se, measured in the same units at 25 C. Intrinsic viscosity, symbol [7 is a measure of the degree of polymerization.

In the examples, values of tenacity in g.p.d., elongation in percent, and initial modulus in g.p.d. (all expressed as T/E/ Mi) are determined upon polyester fibers which have been spun and drawn as indicated. Measurements are made before and after a mock finishing procedure which comprises the consecutive steps of:

(a) heat treating the filaments by boiling them in water for 15 minutes while allowing 3% shrinkage in length,

(b) heating the filaments in an oven at 180 C. for 3 minutes, again allowing 3% shrinkage in length,

(c) heat treating the filaments by boiling them in water for 15 minutes while allowing 1% shrinkage in length, and finally (d) air drying the filaments.

This invention is further illustrated, but it is not intended to be limited, by the following examples in which parts and percentages are by weight unless otherwise specified.

EXAMPLE I Prepaartion of the dimethyl ester of 2,5-diphenylterephthalic acid of the formula:

(a) Preparation of 2,5-dicycl0hexyl-p-xylene A mixture of 106 grams p-xylene, 200 ml. cyelohexane and 20 grams AlCl is cooled to 5 C. and 164 grams cyclohexane is added with stirring. The addition is carried out over a period of 5 hours during which the temperature is held below 9 C. After the addition, the mixture is stirred an additional '7 hours at a temperature below 10 C., and then finally stirred for 10 hours at 20 C. To the mixture is then added 500 ml. of methanol-HCl (4:1) and the pasty product which separates is collected. The solid product is recrystallized from 2 liters of benzeneethanol (1:1), cooling only to room temperature. The product is washed twice with methanol to yield 166.5 grams of product having a melting point of 155 156 C. [previously reported M.P. 152154 C. Chem Ber 89, 2194 (1956)].

(b) Preparation of 2',5-dimethyl-p-terphenyl To 140 grams of 2,S-dicyclohexyl-p-xylene, prepared above, is added 45 grams of 5% Pd-C catalyst and the mixture heated with stirring at 280290 C. until evolution of hydrogen ceases. The molten mixture is cooled, pulverized, and extracted with ethyl acetate using a Soxhlet extractor. The extract is cooled to room temperature and the solid product collected. The procedure yields 99.5 grams of solid having a melting point of 185 187 C.

(c) Preparation of the dimelhyl ester of 2,5-diphenylterephthalic acid A solution of 2000 ml. pyridine, 200 ml. water and 86 grams 2',5-dimethyl-pterphenyl, prepared above, is heated to reflux with stirring, and then a suspension of 264 grams KMnO in 1670 ml. of water is added portionwise. After several hours refluxing, the permanganate color fades and additional permanganate is added until the color is permanent. The mixture is filtered and the filtrate acidified. The precipitate is collected and then washed 3 times in water, and dried to give 99.5 grams of product having a melting point of 297 C. The measured neutral equivalent is 162.1 (theoretical: 157).

The diacid prepared above is converted to the acid chloride by refluxing with an excess SOCl containing a small amount of pyridine as a catalyst. The excess SOCiis then removed and the product treated with anhydrous methanol. After the methanol mixture is refluxed for several hours, one liter of toluene is added and the mixture distilled until the boiling point rises to C., the solution is then cooled to 5 C., the product collected, dried, and triturated with dilute sodium bicarbonate solution. The product is then recrystallized from methanol-dioxane (1:5) to give 152.5 grams of ester melting at 186- 188 C.

EXAMPLE II Preparation of the dimethyl ester of 4,6-diphenylisophthalic acid of the formula:

Q (a) Preparation of 4,6-dicyclohexyl-m-xylene A mixture of 123 grams m-xylene, 200 ml. cyclohexane and 20 grams AlCl is cooled to 3.5 C. and 202 ml. cyclohexene is added with stirring. The addition is carried out over a period of 3 hours during which the temperature is held below 0 C. After the addition, the mixture is stirred an additional 3 hours. To the mixture is then added 500 ml. of methanol-HCI (4:1) and, after stirring for 2030 minutes, 500 ml. benzene and 400 ml. H O is added. The organic layer is separated and washed three times with water. The solution is dried by distillation and then cooled in ice. The solid product is recrystallized from 0.4 liter of benzene-ethanol (1:1), cooling only to room temperature. The product weighs 121 grams and melts at 107-108 C.

(b) Preparation of 4,6'-dimethyl-m-terphenyl To grams of 4,6-dicyclohexyl-m-xylene, prepared as above, is added 43 grams of 5% Pd-C catalyst and the mixture heated with stirring at 300 C. until evolution of hydrogen ceases. The molten mixture is cooled, poured into ethyl acetate, and the catalyst removed by filtration. The ehtyl acetate was removed by distillation and the residual oil crystallized from ethanol. The procedure yields 100 grams of solid having a melting point of 66-68 C.

(c) Preparation of dimethyl ester 0] 4,6-diphenylis0phthalic acid A solution of 200 ml. pyridine, 200 ml. water and 86 grams 4,6'-dimethyl-m-terphenyl, prepared above, is heated to reflux with stirring, and then a suspension of 264 grams KMnO in 1670 ml. of Water is added portionwise. After several hours refluxing, the permanganate color fades and additional permanganate is added until the color is permanent. The mixture is filtered and the filtrate acidified. The precipitate is collected and then washed 3 times in water, and dried to give 70 grams of product having a melting point of 185 -195 C. After recrystallization from aqueous acetic acid the measured neutral equivalent is 159.5 (theoretical: 159).

The diacid prepared above is converted to the acid chloride by refluxing with an excess SOCl containing a The TSR value of 72 is more fully appreciated when it is realized that commercial fibers of polyethylene terephthalate tested in the same test, give TSR values of only 6467.

EXAMPLE V small amount of pyridine as a catalyst. The excess SOCl is then removed and the product treated with anhydrous The general procedure of Example IV is repeated with methanol. After the methanol mixture is refluxed for the exception that different ratios of the two acid comseveral hours, one liter of toluene is added and the mixp ents are used. Polymers are prepared and melt-spun ture distilled until the boiling point rises to 110 C., the to give yarns having the properties in Table 1 below. TSR solution is then cooled to 5 C., the product collected, is measured after mock finishing.

TABLE 1 Acid PMI, Spinning Yarn Draw Draw T/E/Mi, Ratio O. '1ernp., [1;] Ratio Temp, g.p.d./per- TSR BB/DPI C. C. cent/g.p.d.

BB Bibenzoic acid. DPT Diphenylterephthalic acid. dried, and triturated with dilute sodium bicarbonate solu- EXAMPLE VI tion. The product is then recrystallized from methanoldioxane (1:5) to give 42 grams of ester melting at 109- 111 C.

EXAMPLE III Preparation of the dimethyl ester of S-tert-butyl-isophthalic acid of the formula:

To 200 grams of purified S-tert-butylisophthalic acid is added 1.5 liters methanol saturated with HCl. The mixture is heated to reflux temperature and held for 4 hours, and then poured into 2 liters of water whereupon the dimethyl ester separates as a white powder. The product is recrystallized from methanol giving 193 grams of diester having a melting point of 100.3100.8 C. and a saponification equivalent of 124.2 (theoretical: 125.1).

EXAMPLE IV Polyethylene bibenzoate/diphenylterephthalate, 80/20 mole percent A distillation vessel is charged with: Ethylene glycol--15.6 grams, .25 mole Dimethylbibenzoate-2l.6 grams, 0.08 mole Dimethyl ester of 2,5-diphenylterephthalic acid7.5

grams, 0.02 mole Manganous acetate-8.0 milligrams The vessel is heated slowly until all of the methanol and part of the excess glycol is removed by distillation. Then the hot mixture (monomer) is transferred to a polymerization vessel fitted with a vacuum connection along with 0.005 gram of Sb O The mixture is stirred while the temperature is raised to 310 C. and the pressure slowly reduced to 0.9 millimeter of mercury. After 1.3 hours the product is found to have a polymer melting temperature of 265 C. and an intrinsic viscosity of 0.43. Fibers can be drawn from the melt. The melt is cooled, pulverized and heated at 220 C. and 1.6 mm. Hg pressure for 18 hours. The intrinsic viscosity increased to 0.62.

The polymer is melt-spun at 335 C., quenched in air and then drawn 4.3X at a drawing temperature of 142 C. to give fibers having a tenacity of 2.3 g.p.d., a break elongation of 16% and an initial modulus of 118 g.p.d. The fibers are mock finished as previously described, following which the tenacity is found to be 2.2 g.p.d.,, the break elongation 28%, and the initial modulus 74 g.p.d. Measurement of tensile recovery gives a TSR value of 72.

Polyethylene bibenzoate/diphenylisophthalate,

' 80/20 mole percent A reaction vessel is charged with:

Ethylene glycol-31.3 grams, 0.5 mole Dimethyl bibenzoate64.8 grams, 0.24 mole Dimethyl ester of 4,6-diphenylisophthalic acid-24.4

grams, 0.06 mole Manganous acetate-22 milligrams Antimony oxide-l4 milligrams The vessel is heated until all of the methanol and part of the excess glycol is removed by distillation. Then the temperature of the mixture is raised to 300 C. and the pressure reduced to 0.9 millimeter of mercury. After 0.5 hour, the product is found to have a polymer melting temperature of 273 C. and an intrinsic viscosity of 0:82. Fibers and films can be formed from the melt.

The polymer is melt-spun at 345 C., quenched in air, and then drawn 3.7X over a draw pin heated to 120 C. The fibers produced have a tenacity of 2.5 g.p.d., a break elongation of 19% and an initial modulus of 94 g.p.d.

The low rate of crystallization of the polymer is shown by the fact that when immersed in boiling water for 5 minutes the drawn yarn undergoes a shrinkage of 37.7%.

The fibers are mock finished as previously described following which the tenacity is found to be 2.0 g.p.d., the

break elongation 40% and the initial modulus 73 g.p.d. Measurement of tensile recovery gives a T SR value of 71.

EXAMPLE VII Polyethylene bibenzoate/t-butylisophthalate Two polymer batches are prepared using the following compositions as starting material:

Polymer charge A (bibenzoate/t-butylisophthalate, 80/

Ethylene glycol 8 lbs. 13 oz.

Dimethyl bibenzoate 4374 g. Dimethyl ester of t-butylisophthalate 1001 g. Manganous acetate 1.95 g. Antimony oxide 1.30 g.

Polymer charge B (bibenzoate/t-butylisophthalate, 75/

Ethylene glycol 8 lbs. 13 oz.

imethyl bibenzoate 4374 g. Dimethyl ester of t-butylisophthalate 1350 g. Manganous acetate 1.95 g. Antimony oxide 1.30 g.

stirred polymerization vessel, and the temperature raised 7 to 320 C. and the pressure reduced to 0.81.3 millimeters of mercury. Polymerization is continued for 1 hour and then the molten polymer is extruded as a ribbon, solidified, and cut to flake. Polymer A is found to have an intrinsic viscosity of 0.65. Polymer B has an 8 mined from the graph by usual graphical averaging procedures. High TSR values are characteristic of fibers which form wrinkle-resistant fabrics. A more extensive discussion of TSR will be found in an article W. W. Daniels,

9 Textile Research Journal, 30, 656 (1960). avclagemmnslc vlscoslty of about Since many different embodiments of the invention The two polymers are melt-spun, quenched in air, and a drawn using the conditions summarized in the table be. may be f q Wlthout dcpaitlllg f m 6. p1l1'E-and.SCOp.. The properties of the yam are also presented in thereof, it is to be understood that the 1nvent10n is not the table. The TSR values presented are measured after 10 limitcd y the Speclfic lnllstl'fltlons except to the extent a mock finishing procedure, described previously. define-:1 in the following claims.

TABLE 2 Spinning Conditions Spun Yarn Drawing Conditions Yarn Properties Biliz llr l di nge t z d Tenacity Elongation Mi TSR perature (y.p.n1.)

Polymer A 320 500 200 33 .49 3. 0 120 2.70 14. 0 131 67.3 Polymer B 305 503 271 34 .55 3.31 112 2. 42 27. s 35 01. 0

EXAMPLE VIII I claim:

1. A linear random copolyester consisting essentially The general procedure of Example IV is repeated to of the condensation copolymer of ethylene glycol with a prepare polyethylene bibenzoate/t-buty isopht a ate mixture of 70 to 90 mole percent of bibenzoic acid and polymers having various ratios of bibenzoate/t-butylisoto 10 ol percent of a b lky, asymmetrically subphthalate units. Polymers are prepared and melt-spun stituted phthalic acid selected from the group consisting to give yarns having the properties shown in the table 30 of 2,5-diphenylterephthalic acid, 4,6-diphenylisophthalic below. acid and S-tert-butyl-isophthalic acid.

TABLE 3 Acid PM'I, Spinning Yarn Draw Draw T/E/Mi, Ratio 0. Temp, [1;] Ratio Temp, g.p.d./per- TSR BB/t-BuI C. C. cent/god.

BB =Bibenzoic acid. 12-13111=tert.-butylisophthalic acid.

The TSR of a yarn sample is determined by mounting 2. Fibers of the copolyester defined in claim 1 having a 10-inch length of the yarn on a tensile tester with rean intrinsic viscosity of at least 0.3, the intrinsic viscording chart (commercially available from the Instron cosity being determined for a 25 C. solution of the co- Engineering Corporation, Quincy, Mass.) and also polyester in methylene chloride-20% trifiuoracetic equipped with a circulating water bath which can be 45 acid solvent. raised and lowered. The water bath, maintained at 40 3. Yarn of a linear condensation copolyester of ethyl- C., is raised to immerse the yarn. After the yarn has ene glycol with a mixture of to 70 mole percent of been immersed for 2 minutes without tension it is stretched, bibenzoic acid and 10 to 30 mole percent of a bulky, asymin the water bath, at an elongation rate of 1 inch per metrically substituted phthalic acid selected from the minute. Upon reaching the desired total elongation, the 50 group consisting of 2,5-diphenylterephthalic acid, 4,6-disample is held at constant length for an additional 2 phenylisophthalic acid and S-tert-butyl-isophthalic acid, minutes and the water bath is removed. The load on the having a polymer melting temperature of 225 to 311 yarn is then reduced to a value of 0.042 g.p.d. and the C., the yarn having a tenacity of at least 2 grams per yarn is allowed to retract. Percent recovery is calculated denier and aTSR value of about 55 to 72. from the formula: 55

References Cited 1% of retraction elongationx UNITED STATES PATENTS This procedure is carried out for elongations of 0.5, 3=265 762 8/1966 Qulsenberry 26075 1, 2 and 3%, and a graph is prepared by plotting the 60 percent recovery against total elongation in the range 03%. TSR values are average percent recovery values from the range 03% elongation which may be deter- WILLIAM H. SHORT, Primary Examiner.

R. T. LYON, Assistant Examiner, 

